Both natural and synthetic molecular sieve materials (e.g., zeolites, aluminophosphates, or mesoporous materials) have been demonstrated to have catalytic properties for various types of hydrocarbon conversion and are utilized in a number of industrial processes. These materials are characterized by ordered, porous crystalline structures that can be determined by X-ray diffraction (XRD). Because the pores of these materials are of molecular dimensions, selective size-exclusive adsorption is possible, hence the name, “molecular sieves.”
Molecular sieves are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature. According to this classification, framework type zeolites and other crystalline microporous molecular sieves, for which a structure has been established, are assigned a three letter code and are described in the “Atlas of Zeolite Framework Types,” Sixth Revised Edition, Elsevier, 2007.
Molecular sieves identified by the International Zeolite Association as having the framework type AFX are known. One example of an AFX framework type material is zeolite SSZ-16.
U.S. Pat. No. 4,508,837 discloses zeolite SSZ-16 and its preparation in the presence of organic nitrogen-containing compound derived from 1,4-di(1-azoniabicyclo[2.2.2]octane) lower alkanes, wherein the lower alkane portion of the organic nitrogen-containing compound has from 3 to 5 carbon atoms.
U.S. Pat. No. 5,194,235 discloses a method for preparing zeolite SSZ-16 using a DABCO-Cn-diquat organic structure directing agent where n is 3, 4, or 5. It is reported that the as-prepared SSZ-16 zeolite has a SiO2/Al2O3 molar ratio that is typically in a range of 8 to 15.
R. F. Lobo et al. (Chem. Mater. 1996, 8, 2409-2411) report that zeolite SSZ-16 can be only synthesized in a restricted range of SiO2/Al2O3 molar ratios.
U.S. Pat. No. 8,562,942 discloses the synthesis of an AFX framework type zeolite in the presence of 1,3-bis(1-adamantyl)imidazolium cations at a SiO2/Al2O3 molar ratio of 35 and a hydroxide/silica molar ratio of 0.05 for the reaction mixture. At higher SiO2/Al2O3 molar ratios (e.g., 50 or 100), materials other than AFX framework type zeolites were produced.
U.S. Patent Application Publication No. 2016/0137518 discloses an aluminosilicate zeolite having at least 90% phase pure AFX framework and a SiO2/Al2O3 molar ratio of 12 to 50.
According to the present disclosure, an AFX aluminosilicate zeolite having a SiO2/Al2O3 molar ratio of greater than 50 to 100 is disclosed.